In wind turbines, the nacelle houses components and systems necessary for converting mechanical energy into electricity. The components may range from heavy duty generators, gearboxes, brakes and transformers to small electronic components. These systems and components generate a significant amount of heat inside the nacelle. This heat has to be dissipated to outside ambient air for efficient operation of the nacelle components.
State of the art systems for removing heat from power electronics and heavy duty components include pumps or fans for circulating water or air between a region of relatively high temperature in, on or near the component or system to be cooled and a region of relatively low temperature, where heat is typically dissipated through fins or tube bundles to ambient air.
Heat from power electronics is normally dissipated to outside ambient air by a water cooled system, in which water is circulated between a relatively cold plate and a surface of the power electronics module.
It will be appreciated that the above air-to-air heat exchangers and air-to-water heat exchangers require pumps or fans as well as piping arrangements to circulate water. The cooling systems are consequently bulky, whereby installation thereof is a complex and expensive task due to the limited space available inside wind turbine nacelles. Moreover, systems including pumps and fans are susceptible to wear and ultimately break-down, which may result not only in interruption of the operation of the wind turbine, but also in damage to heavy duty components or electronics due to overheating thereof.
Further, the amount of heat to be removed from heat-generating components in wind turbine nacelles varies in dependence of external conditions, such as ambient temperature, as well as in dependence of the load on the wind turbine during operation. For example, when the wind turbine operates at high loads the amount of heat generated within the generator and within power electronics in the generator is higher than when the wind turbine operates at low loads, where less power is fed into the generator. Air-to-air or air-to-water heat exchangers are not accurately controllable in all circumstances, and though they are generally designed to provide a sufficient degree of heating, their energy consumption is often excessively high, because, as a safety measure, they are often adapted to provide an unnecessarily high degree of cooling. Yet, the electronic modules, such as in particular printed circuit boards (PCBs) heat up significantly due to the high power dissipations from e.g. generators, transformers and like components, which are typically housed within an enclosed space. With varying operating conditions, the PCBs can be heated and cooled quickly over a period of time, and due to the coefficient of thermal expansion mismatch within the PCBs, failures in the solder joints can occur with the repeated expansion and contraction of the materials within the PCBs.